Multifocal lens



Sept" 1927" E. D. TILLYER MULTIFOCAL LENS Filed Oct. 20, 1924 v gclgglr gfiHen s- W a a 0,0 5 -V T- V w 4 fig Mm anauanzazm Patented Sept. 6, 1927.

UNITED STATES PATENT OFFICE.

EDGAR D. TILLYER, OF SOUTHIBRIDGE This MASSACHUSETTS, ASSIGNOR T AMERICAN OPTICAL COMPANY, OF SOUT HBRIDGE, MASSACHUSETTS, A VOLUNTARY ASSOCIA- TION OF MASSACHUSETTS.

MULTIFOCAL LENS.

Application filed October '20, 1924. Serial No. 744,781.

invention relates to improvements in ophthalmic lenses and has particular reference to formed a multifocal lens the provisions of Prior to of two pieces of material.

my invention a number of attempts have been made t index.

0 produce different refractive. In such cases, the additions for the reading and intermediate portions have been obtained through the effect of the combination One vention which is formed of two pieces Another object of the invention is to proof the different refractive indices. of the principal objects of this in* is the provision of a trifocal lens of material.

vide such a trifocal lens wherein the segment is lnserted 1n the manor blank, a portion of its outer surface being continuous with that of the blank and the remainder having a different curve.

Anotherobject is to the formation of such plurality of finished lenses may Other objects and advantages should be apparent from the provide a blank for lenses from which abe produced.

following description taken in connection with the accompanying drawings, whereln Figure 1 is an elevation of a finished lens embodying the invention.

Figure 2 is a sectional viewon the line 2-2 of Figure 1. 3

Figure?) is a sectional view through a "partly finished blank.

Figure 4 is a similar View illustrating the 'nextstep in the production of the blank.

re 5 is a similar View through the finished blank, and

Figure 6 is an elevation of said finished blank.

Similar reference characters designate cor responding, parts throughout the several views.

In Figures 1 and 2 an ophthalmic lens i gnates embodying the present invention has-been illustrated.

The reference character 10 desof the blank, the

the main portion is suitably ground 11 of which at 12 and secured within the recess is a minor portion or what is commonly known 'as a segmen t 13. The two'pieces 10 and 13 are trifocal lenses by 1nsert-' lng two segments into a major blank, each the lower part of the segment;

while the segment 20 polished surface 21 ferent curvature 16 suitably calculated to give a stronger optical power than the remainder of the lens. From this, itwill be seen that three different optical powers have been formed, the largest portion being the weakest of the three, a second intermediate field being defined by the extreme edge 17 of the segment and by the line 15 previously pointed out. The optical addition of this intermediate field is formed by the bottom curvature 12 and a combination of the-two different refractive indices "at, that point. In view of the fact that the surface curve 16 is ground stronger than the continuous curve 14, a reading portion is produced on Referring now to Figures 3, 4, 5, and 6, a practical process of manufacture is illus tra-ted step b step for the production of an improved bi ocal lens of the above charac ter. The circular blank 18 of crown glass is provided on one of its surfaces with a ground and polished spherical recess 19-, having a groun and of the same degree of. curvature as the recess 19 is also produced. The segment 20 is then secured within the recess 19 either by cement or fusing, the

latter being the preferable way .of doing it.

After the segment/ is thus secured in the blank,the blank is mounted in a lens grindto a line such as is indicated by i ing machine and surfaced to the curves 22 v and '23, respectively, the centralcurvature 23 being of a sho ter radius than the curvature 22 and occupying only a portion of the total area of the segment. The blank 18 may then be cut-upon the diametric line 247-25 from each of which, sections a finished lens maybe cut asindi'cated by the dotted lines 26.

The method of forming and uniting the button 20 and-the recessed blank 18 is the so such changes falling within the scope of the lppended claims without departing from samefas is known'to those skilled in the art for roducing regular fused bifocals. After the button is secured within the recess 19 the two curves 22 and 23 may be produced upon machinery such as has been used for forming ordinary onepiece bifocals in tar get formation. Ordinarily such machines embody a spindle which may be set to a de-' siredangle and adapted to rotate an annular abrading tool upon'the lens surface whilethe blank itself is rotated on another spindle. The two curves 22 and 23 may be prov duced simultaneously or each in aaseparate operation as desired.

From the foretgoing-it'will be evident that an improved tri whereln an intermediate vision field-is dis osed between the distance field and the reading field; The construction is such that a t e spirit of the invention.

ocal lens has been producedv Havin thus described the invention, .what is claime is 1-. A-multifocal lens comprising a focal field of a'single piece of glass having a dis-1 tance curvature on the multifocal side thereof, a second focal field comprised of a separate piece of lass of different index of refraction from the'first iece of' lasssuperimposed onthe first piece of g ass and aving the same surface curvature on the multifocal side thereof as the first piece 'of glass, and a third focal'field composed of the said two pieces of glass but having a difierent surface curvature on the said multifoca-l p,

side from that of the other fields. I

2. A multifocal lens comprising a focal field of a single piece of glass havm a cur.-

rvatur'e on the multifocal side thereo a second field comprised of a separate pieceof glass of .a different index of refraction from the first piece of glass superim o'sed on' the first piece of glass and having t e same surface curvature on the multifocal side thereof as the first piece of glass, a third field composed of the said-two pieces of glass but having a different surface curvature on the said multifocal side from that of the other fields and a curvature on the side opposite the multifocal side adapted to give the repaired prescription value to each'of the said ocal fields.

EDGAR j).- TILLYER. 

